Examples of electronic devices include various scales of integrated circuits and various types of semiconductor devices and chips thereof. As means for realizing a three-dimensional circuit configuration in electronic devices of this type, there has been adopted a method of disposing LSIs on a circuit board and connecting them by means of wire bonding or the like. However, this method increases the mounting area with the number of LSIs, so that the signal delay between LSIs increases because of an increase in wiring length.
Accordingly, there has been proposed a TSV (through-silicon-via) technology of providing a circuit board with a large number of through electrodes and stacking these circuit boards. Japanese Unexamined Patent Application Publication Nos. 11-298138, 2000-228410, 2002-158191, 2003-257891, and 2006-111896 disclose a through electrode formation technology essential for the TSV technology. The superiority of the TSV technology over the wire bonding is as follows.
At first, in the wire bonding, the number of connections is limited to 100 to 200, but the use of the TSV technology allows arrangement of connecting through electrodes at intervals of the order of μm, making it possible to increase the number of connections to several thousand.
In addition, there can be obtained advantages as follows: since connection distance can be minimized, it is less likely to be affected by noise; since parasitic capacitance and resistance are low, it is possible to reduce delay, attenuation, or waveform degradation; an additional circuit is not required for amplification or electrostatic breakdown protection; and with these advantages, there can be realized high speed action and low power consumption of the circuit.
By using the TSV technology, it is possible to obtain not only an electronic device including an analog or digital circuit, a memory circuit such as a DRAM, a logic circuit such as a CPU, or the like, but also an electronic device including different types of circuits such as an analog high frequency circuit and a low frequency, low power consumption circuit prepared in different processes and stacked together.
By applying the TSV technology to a three-dimensional integrated circuit (3D IC), many functions can be packed into a small footprint. In addition, important electrical pathways between devices can be dramatically shortened to increase processing speed.
In the TSV technology, however, since substrates formed with through electrodes have to be stacked, it is necessary to align the through electrodes between the substrates to be stacked. Heretofore, an image processing technology has been used for the alignment. However, since the through electrodes are arranged at intervals of the order of μm, it is difficult for the image processing technology to achieve accurate alignment. Even if the alignment can be achieved on a screen, there is still a possibility of causing displacement between the substrates in an actual process.